Dosing just alk?

[goldenhurricane2]

So what was the conclusion with this? I've run into a similar issue with my alk running low but my Ca and Mg relatively stable. I haven't dosed in the past, but I'm going to begin dosing for alk since I can tell that it's beginning to affect some of my SPS.

 

[Randy Holmes-Farley Verified Community Expert]

So what was the conclusion with this? I've run into a similar issue with my alk running low but my Ca and Mg relatively stable. I haven't dosed in the past, but I'm going to begin dosing for alk since I can tell that it's beginning to affect some of my SPS.

What is the question exactly?

It is not correct that alk only is depleting (even if it seems that way from short term monitoring; alk does always drop faster on a percentage basis) , but it can be the case that some salt mixes start with so much excess calcium that if you want to keep a lower level in the tank than the mix adds, that you may need less or even no calcium added.

 

[Havasuviking]

My alk drops about .3/day and cal is very stable. I just dose alk. No problems to date.

 

[Randy Holmes-Farley Verified Community Expert]

My alk drops about .3/day and cal is very stable. I just dose alk. No problems to date.

However, calcium is likely also declining and your kit just cannot detect the expected drop of about 2 ppm per day.

The only way that isn't the case is if you use a sulfur denitrator, or if nitrate is rising rapidly.

 

[goldenhurricane2]

What is the question exactly?

It is not correct that alk only is depleting (even if it seems that way from short term monitoring; alk does always drop faster on a percentage basis) , but it can be the case that some salt mixes start with so much excess calcium that if you want to keep a lower level in the tank than the mix adds, that you may need less or even no calcium added.

Ok this may answer my question - I use Red Sea Coral Pro Salt. So you're saying that it could be possible that the Ca replenishment is occurring through water changes but that the KH usage may be too much to be replenished by water changes alone?

 

[Randy Holmes-Farley Verified Community Expert]

Ok this may answer my question - I use Red Sea Coral Pro Salt. So you're saying that it could be possible that the Ca replenishment is occurring through water changes but that the KH usage may be too much to be replenished by water changes alone?

That would depend on the target values you are maintaining in the aquarium, but in theory it can be true. In general, there are few ways that alk gets depleted that calcium is not also depleted. Two are rising nitrate and sulfur denitrators. I discuss what possible reasons they may be for an imbalance in the article linked below, and there are not a lot of them:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

The other issue is that makes many people think (incorrectly) that they have alk demand and not calcium is simply that the calcium decline, on a percentage basis, is far lower and harder to detect with a kit than is the alk decline.

In general, I expect that most reefers who think they have only alkalinity declines actually dosed a properly designed two part for calcium and alkalinity, they would not see a rise in calcium.

 

[Havasuviking]

However, calcium is likely also declining and your kit just cannot detect the expected drop of about 2 ppm per day.

The only way that isn't the case is if you use a sulfur denitrator, or if nitrate is rising rapidly.

That might be true but I don't see the need to dose Ca when it decreases from 435 to 420 in a week.

 

[Potatohead]

That might be true but I don't see the need to dose Ca when it decreases from 435 to 420 in a week.

Let's do some math.

You start at 435, and losing 15 ppm per week. You use a salt with high calcium levels, let's be really generous and say 480, and you do 10% water changes a week. New water is 480, tank is at 420. Doing a 10% with this very high calcium salt only brings the tank up to 426. Then over the next week you lose another 15 to 411, and so on.

 

[Randy Holmes-Farley Verified Community Expert]

That might be true but I don't see the need to dose Ca when it decreases from 435 to 420 in a week.

Ok. That's certainly a fine approach (recognizing the longer term issue in the post above this one)

But that is very different than concluding only alk is dropping and that calcium is "stable"

That leads to all sorts of incorrect conclusions when other reefers read that.

 

[goldenhurricane2]

That would depend on the target values you are maintaining in the aquarium, but in theory it can be true. In general, there are few ways that alk gets depleted that calcium is not also depleted. Two are rising nitrate and sulfur denitrators. I discuss what possible reasons they may be for an imbalance in the article linked below, and there are not a lot of them:

When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2004-12/rhf/index.htm

The other issue is that makes many people think (incorrectly) that they have alk demand and not calcium is simply that the calcium decline, on a percentage basis, is far lower and harder to detect with a kit than is the alk decline.

In general, I expect that most reefers who think they have only alkalinity declines actually dosed a properly designed two part for calcium and alkalinity, they would not see a rise in calcium.

That may be my issue, so I'll stick with 2 part - Thanks for your help!

 

[Havasuviking]

Ok. That's certainly a fine approach (recognizing the longer term issue in the post above this one)

But that is very different than concluding only alk is dropping and that calcium is "stable"

That leads to all sorts of incorrect conclusions when other reefers read that.

Not looking to get into an argument here. Just saying that if it is that important for your tank be exactly at the same Ca level everyday, then go for it. All I am saying that I want to enjoy my reef tank, and my tank stays within accepted levels everyday.

 

[Randy Holmes-Farley Verified Community Expert]

That may be my issue, so I'll stick with 2 part - Thanks for your help!

You're welcome.

Happy Reefing.

 

[Randy Holmes-Farley Verified Community Expert]

Not looking to get into an argument here. Just saying that if it is that important for your tank be exactly at the same Ca level everyday, then go for it. All I am saying that I want to enjoy my reef tank, and my tank stays within accepted levels everyday.

I'm not trying to say it doesn't.

You have pretty low alk demand (and so pretty low expected calcium demand, maybe 2 ppm per day) and water changes with a high calcium mix may maintain calcium for some significant period of time.

 

[Clownfishy]

Following this thread with interest as I have posted a similar issue here
https://www.reef2reef.com/threads/alkalinity-magnesium-dropping.366819/

What is interesting, I am also using Reef Crystals performing a 10% water change each week and beginning to think this maybe contributing to what looks like Alk dropping and Calcium stable. I seem to get through a lot of Magnesium and I am currently dosing Tropic Marin Bio Magnesium daily to raise this. Just finished reading Randy's article on the imbalance and it talks about Magnesium being used in place of Calcium. @Randy Holmes-Farley , would you mimd expanding a little on what type of corals or circumstances Magnesium is used instead of Calcium?

 

[Randy Holmes-Farley Verified Community Expert]

Following this thread with interest as I have posted a similar issue here
https://www.reef2reef.com/threads/alkalinity-magnesium-dropping.366819/

What is interesting, I am also using Reef Crystals performing a 10% water change each week and beginning to think this maybe contributing to what looks like Alk dropping and Calcium stable. I seem to get through a lot of Magnesium and I am currently dosing Tropic Marin Bio Magnesium daily to raise this. Just finished reading Randy's article on the imbalance and it talks about Magnesium being used in place of Calcium. @Randy Holmes-Farley , would you mimd expanding a little on what type of corals or circumstances Magnesium is used instead of Calcium?

Some magnesium always gets into aragonite in place of some of the calcium, but not typically more than 1/10th of the calcium, and in some corals, it is almost none.

Coralline algae actually deposits a different crystal form of calcium carbonate, calcite. It takes up a lot of magnesium, close to 1/10th of the calcium or a bit more.

 

[becon776]

well here we go... no water changes i tjese graphs. tank is 1yo so calc algae is still building. i add NO Ca and NO mg (yet). i have to dos 12ml/day bionic to keep alk level.
also should be mentioned that i run a triton approved fuge on this reefer 450.